1. Field of the Invention
The present invention relates to an apparatus for facilitating disaster recovery.
2. Description of the Related Art
A disaster (e.g. a computer virus; a terrorist attack on a building; a natural disaster such as an earthquake etc.) can pose serious risks to business operations. For example, data loss; financial losses (e.g. loss of revenue); long term losses (e.g. loss of market share); recovery costs (e.g. cost of replacing infrastructure, computer hardware/software etc.) etc.
Thus, many businesses today have disaster recovery (DR) systems that can be put in place in the event of a disaster. An example of a prior art DR system 100 is shown in FIG. 1, wherein a primary site 105 (e.g. a factory, a bank etc.) comprises a computer system 110 operable to manipulate data e.g. typically by performing write operations. However, it should be understood that any number of other operations can be performed e.g. software update etc. It should also be understood that typically, read operations are not subject to DR.
The data represents a primary storage image 115 stored on one or more primary storage devices e.g. shared storage arrays; tape libraries; disk storage etc. at the primary site 105. In response to the write operation, the primary storage device is updated by issuing the write operation to the primary storage device.
The DR system also comprises a secondary storage image 125 located at a secondary site 120. Preferably, the secondary site 120 is located remotely from the primary site 105 such that in the event of a disaster (e.g. an earthquake), the secondary site 120 is not affected.
The secondary storage image 125 is a replica of the primary storage image 115 and is stored on one or more secondary storage devices e.g. shared storage arrays; tape libraries; disk storage and the like at the secondary site 120. It should be understood that the secondary storage image need not be an exact replica of the primary storage image. For example, the secondary storage image can comprise a subset of the primary storage image (e.g. wherein the subset comprises the most important data of the primary storage image). The one or more secondary storage devices correspond to the one or more primary storage devices. It should be understood that a direct correspondence need not occur. It should be understood that the one or more secondary storage devices are always online.
In response to a write operation against the primary storage image 115, the primary storage image 115 is updated. Furthermore, the write operation is transmitted over a data transportation system 130 (e.g. Ethernet; fibre channel etc.) to the secondary storage image 125.
Preferably, an acknowledgement indicating receipt of the write operation is transmitted to the computer system 110. In response to receipt of the acknowledgement, a user at the computer system 110 can perform further operations against the primary storage image 115. In response to receipt of the write operation, the secondary storage image 125 is also updated by issuing the write operation to a secondary storage device.
In the event of a disaster, it is ensured that a last completed write operation has been executed against the secondary storage image 125 (i.e. wherein the write operation is the last complete write operation before the disaster occurred). The secondary storage image 125 is then used for DR purposes (e.g. data associated with the secondary storage image 125 is read; data associated with the secondary storage image 125 is used to recover some/all of the primary storage image 115 etc.).
Costs associated with maintaining a DR system can be very high. For example, there are financial and environmental costs associated with supplying energy to the secondary site 120 for powering the secondary site 120, powering and cooling the secondary storage devices etc. In another example, financial costs are associated with housing the secondary site 120. In yet another example, financial costs are associated with housing the secondary storage devices i.e. as cooling equipment for the secondary storage devices can require space, the secondary storage devices cannot be densely housed.
As a DR system may be used rarely, if at all, a business can find these costs disproportionate. Furthermore, if secondary storage devices at the secondary site 120 are low performance storage devices, a write operation executed against the secondary storage image 125 can take time to complete. This is due to the low performance of the secondary storage devices.
There is a need to provide a DR system which is cost effective, efficient and highly available.